Control of electric motors for operation of wing flaps of aircraft



D. P. ALEXANDER 2,498,231 CONTROL OF ELECTRIC MOTORS FOR OPERATION Feb.21, 1950 OF WING FLAPS 0F AIRCRAFT 2 Sheets-Sheet 1 Filed Jan. 10, 1946\jl lll'w //2 venor Feb 21, 1950 D. P. ALEXANDER 2,498,231 CONTROL OFELECTRIC MOTORS FOR OPERATION OF WING FLAPS 0F AIRCRAFT Filed Jan. 10,1946 2 Sheets-Sheet 2 Mumfor DAVID PoRTEoUS ALEXAMDE R QQRQM PatentedFeb. 21, 1950 CONTROL OF ELECTRIC MOTORS FOR glfigTION OF WING FLAPS OFAIR-.-

David Porteous Alexander, Farnborough, England Application January 10,1946, Serial No. 640,332

In Great Britain January 10, 1945 4 Claims. 1 This invention relates toimprovements in the control of electric motors for operating the wingflaps of aircraft.

In general, the control of wing flaps of aircraft is left in the handsof the pilot and he 5 is above the safe permissible limit then the motoris trained to operate them only when the speed or motors will beprevented from lowering the of the aircraft is at or below a safe speed.flaps or will lower the flaps an amount depend- In the operation of thewing flaps by electric ing on the aerodynamic torque developed by themotors, however, it is desirable to co-ordinate air load on the flapswhich is opposing the subthe rate of flap movement with the rate of 10,stantially constant torque developed by the motor change of lift, dragand trim of the aircraft or motors. If the flaps are being lowered orand so. lighten the pilots duties. It is highly have been lowered andthe aircraft speed indesirable, therefore, to have a control systemcreases above the safe permissible limit then the which will prevent orlimit flap movement when increase in aerodynamic torque developed by thethe speed of the machine exceeds the safe limit; flaps will oppose orovercome the torque develand permit the air load acting on the flaps toreoped by the motor or motors and cause the motor tract them if thespeed limit is exceeded after or motors to stop lowering the flaps orcause the the, flaps have been lowered and to allow the flap to beretracted and the motor or motors to flaps to be relowered automaticallywhen the air be driven in the reverse direction until a balance speed isreduced to the safe limit if the flaps is struck. Conversely if thespeed of the airdown position has remained selected. craft thendecreases to or below the safe permis- According to the presentinvention means for sible limit, the motor or motors will lower theelectrically operating aircraft wing flaps comflaps. The predeterminedvalue of the current prises one or more separately excited reversibleand therefore the torque of the motor or motors D. C. motors actuatingthe wing flaps through can be adjusted by a variable resistance arrangedreversible gearing and a current regulator conin parallel with the coilof the regulator or by sisting of a resistance and electro-magneticarranging a series of tappings in the coil itself. means, saidresistance and electro-magnetic The value of the controlled current andso the means being so connected in the armature cirtorque of the motoror motors can be varied cult of the motor or motors that the, armaturesynchronously with the position of the flaps to current and consequentlythe torque of the motor counterbalance the increase in aerodynamic ormotors is maintained at a predetermined contorque as the flaps arelowered. A variable restant value irrespective of line voltagevariasistance connected in parallel with the coil or tions and air loadson the flaps. The current with the presetting resistance and linked withregulator comprises a carbon pile resistance adthe flaps can be arrangedto vary the value of the justably spring loaded to a minimum resistancecontrolled moment and therefore the torque of and an electric magnetwhose coil is arranged in the motor or motors according to flapposition. series with the carbon pile in the armature cir- One form ofthe invention will now be described cult of the motor or motors andwhose armature by way of example only, with reference to the is.arranged to increase the resistance of the caraccompanying drawing towhich: bon pile in opposition to the spring by reducing Figure 1 is adiagram for electrically operated the loading between the elementscomposing the aircraft wing flaps. carbon pile. The relationship of theforce on Figure .2. is a section of a current regulator. the armaturedue to the magnetic flux of the In Figure 1 a D. C. electric motor I isarranged coil and the force of the spring is such that to operate wingflaps 2 and 3 of an aircraft (not for a predetermined value of theexciting current shown) through a reversible gearing 4. The the forcesare approximately balanced for every motor I is separately excited andis reversible position of the armature over its working range. havingits field winding 5 connected through a Thus with such a relationshipthe regulator will control switch 6 to a D. C. supply 1 throughconautomatically adjust the resistance to maintain 5D d t rs B, 9 d [0,Th armature i t of the current in. the coil substantially constant atthe motor 1 is connected to the control switch 6. the predeterminedvalue. Any tendency for the by conductors ll, l2 and 13. current in thecoil to depart from this value will A current regulator 14 (see Figure2) has its cause a change in the resistance of the carbon operating coil15 and its carbon pile resistance pile suflicient to correct for thisdeparture and I6 (consisting of carbon elements IBa) connected somaintain the current in the coil and in the armature circuit of themotor or motors substantially constant.

Since the armature current to the motor or motors is substantiallyconstant and the motor or motors is or are separately excited, thetorque of the motor or motors will be substantially constant. Underthese conditions if an attempt is made to lower the flaps when theaircraft speed in series. core I! and an armature l8 of magneticmaterial (1. e. iron) which is carried on the centre of a The coil [5 isarranged on an iron.

3 which is arranged within a ceramictube 20 carried in a bodyzl, is heldin compression between the disc spring I9 and an adjusting cap 22secured to the body H.

The regulator I4 is connected between the con- 7 ductors I2 and I3 inseries with the armature of the motor I. A variable resistance 23 isarranged in parallel with the operating coil I5. Since the motor I isseparately excited, the torque developed will be proportional to thearmature current. The armature current is, however, regulated by thecurrent regulator M. The operating coil I actuates the armature I8against the force exerted by the spring Iii-which acts to compress theelements lBa forming the pile It. The relationship of the force on thearmature I8 due to the magnetic flux of the coil i5 and the force of thespring I9 is such that for one predetermined value of the excitingcurrent the forces are approximately balanced for every position of thearmature I8 over its working range. Thus with such an arrangement theregulator It will adjust its resistance automatically to maintain thecurrent in the coil I5 substantially constant at the predeterminedvalue. Any tendency for the current in the coil I5 to depart from thepredetermined value will cause a change in the resistance of the pile l6sufficient to correct for this departure and so maintain the current inthe coil I5 and in the armaturecircuit of the motor I, substantiallyconstant. The torque of the motor I will therefore be substantiallyconstant irrespective of line voltage variations and torque variationsdue to the air load on the flaps 2 and 3. The predetermined value of thecurrent supplied to the armature of the motor I (thus the torque of themotor I) can be adjusted by the variable or presetting resistance 23which is arranged in parallel with the coil I5 of the regulator I4; Thevalue of the controlled current can be varied synchronously with theposition of the flaps 2 and 3 between the flaps up and flaps downposition by the variable resistance 24 connected in parallel with theresistance 23 and coil I5 by conductors 25 and 26 and controlled by alinkage 21 actuated by the flaps 2 and 3. Thus the torque of the motor Ican be varied from a minimum in the flaps up position to a maximum inthe flaps down position to allow for the flap torque increase as theflaps 2 and 3 are lowered. The maximum value must not, however, increasethe torque of the motor I beyond a value just sufiicient to maintain theflaps 2 and 3 in the down position at the highest safe speed forlowering the flaps 2 and. 3. I

In operation the control switch 6 is actuated to start the motor I tolower or raise the flaps 2 and 3. If the control switch 6 has beenactuated to lower the flaps 2 and 3 and the speed of the aircraft isabove the safe permissible flap lowering speed the motor I will attemptto move or move the flaps 2 and 3 an amount depending on the magnitudeof the air load on the flaps (flap flaps 2 and 3 to stop moving or causethe flaps 2 and 3 to retract and drive the motor I in a reversedirection. If the control switch 6 has not been operated to change'therequired position of the flaps and the speed of the aircraft then falls4 to or below the safe permissible speed the motor I will relower theflaps 2 and 3.

When more than one motor is provided for lowering and raising the flaps,it will be necessary to include a synchronising system to keep themovement of the motors and flaps synchronised.

The scope of the patent is not determined only by the appendant claimsbut it extends to and includes all the features hereinbefore describedand illustrated in the accompanying drawings.

I claim:

1. Electrical control gear for aircraft-wing flaps comprising areversible separately excited direct current motor, means includingreversible reduction gearing for coupling the motor to the wing flaps ofan aircraft, direct current supply leads for the motor armature, amanually oper able reversing switch having a flaps up and a flaps downposition interposed between the supply leads and the motor, a carbonpile resistance connected in series between the switch and the motor,spring means acting to compress the carbon pile, an armature on saidspring means, and an electromagnet having a winding con- I nected inseries with the carbon pile between the winding of the electromagnetwhereby the extent to which in operation the action of the spring meanson the carbon pile is opposed and therefore the value at which thecurrent to the motor is maintained substantiall constant is adjustable.

3. Electrical control gear for aircraft wing" flaps, as claimed in claim1, wherein the winding of the electromagnet is tapped and means areprovided for connecting difierent tappings in the switch-carbonpile-motor circuit, whereby the extent to which in operation the actionof the spring means on the carbon pile is opposed and therefore thevalue at which the current to the' motor is maintained substantiallyconstant is adjustable.

4. Electrical control gear for aircraft wing flaps, as claimed in claim1, wherein a variable resistance is connected in parallel with thewinding of the electromagnet and means are provided for coupling saidvariable resistance with the wing flaps for adjustment in accordancewith the position of the latter so that the magnitude of said variableresistance is at a maximum when the flaps are up and at a minimum whenthe flaps are fully lowered, whereby the extent to which in operationthe action of the spring means is opposed and therefore the value atwhich the current to the motor is maintained substantially constant ismadeclependent upon the position, and thus the air loading, of theflaps.

DAVID PORTEOUS ALEXANDER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 425,883 Hunter Apr. 15,1890

2,411,139 Roy et al NOV. 12, 1946

